Light-weight, flexible, and low-cost organic electronic devices are a growing market. Organic light emitting diode (OLED) displays for smart phones have been commercialized. Organic thin film transistors (OTFTs) are basic units in organic integrated circuits and are an important elemental organic electronic device. For example, these elements are employed in radio-frequency identification (RFID) tags and sensors and are used to drive individual pixels of active matrix displays. Low-power complementary circuits use positive and negative gate voltages to switch transistors, requiring p- and n-channel transistors. However, n-channel OTFTs are underdeveloped relative to their p-channel counterparts. N-channel OTFTs suffer from poor stability in air. Typically, two methods are used to fabricate OTFTs, namely, vacuum deposition and solution processing. Vacuum deposition techniques are more expensive to perform than are solution processes that are compatible with roll-to-roll or ink jet printing techniques for large area deposition on flexible substrates. Field effect mobility is the most important parameter for OTFTs, and OTFTs with high field effect mobility have wide applications. For example, OTFTs with field effect mobility higher than 1 cm2V−1s−1 can be used to replace thin film transistors of amorphous silicon.
An OTFT typically consists of three electrodes (gate, drain, and source), a dielectric layer, and an organic semiconductor layer. OTFTs are interface devices whose performance strongly depends on the interface between an organic semiconductor and a dielectric regardless of the manner that the organic semiconductor is fabricated, whether by vacuum-deposition or solution-processing. Therefore, it is crucially important to control the structures and properties of the dielectric surface of the OTFT during device fabrication. Hence, to achieve OTFTs that exhibit high field effect mobility and robust environmental stability, there remains a need to develop a general dielectric surface for high-performance p- and n-channel OTFTs that can be fabricated using either vacuum deposition or solution processing.